The present invention relates to a method for identifying an object within a protective zone with a protective device for a vehicle, the device comprising an optical sensor installed on the vehicle for locating objects within an area of coverage, wherein at least one protective zone located within the area of coverage is preset in the optical sensor, wherein the optical sensor generates a switching signal if an object is detected in the protective zone.
Protective devices of this type, which operate in a non-contacting manner, are used in particular for the protection of persons. The protective device in question is provided with an optical sensor installed on a vehicle, in particular a driverless transportation system. This protective device is designed to prevent collisions by monitoring the area in front of the vehicle with an optical sensor if the vehicle is in motion. In the process, the optical sensor analyzes whether an object is detected within a protective zone. If the object is detected within a protective zone, the optical sensor generates a shut-down command which stops the vehicle in the protective zone and prevents a collision between the vehicle and the object entering the protective zone, in particular a person.
The problem with systems of this type is that the vehicle, in particular a driverless transport system, moves along predetermined driving routes, for which the surroundings can change constantly. To ensure a secure protection against collision, it is desirable to change the dimensions of the protective zone, such that the protective zone corresponds to the surrounding conditions and the speed of the vehicle. For example, if the vehicle travels at a high speed, the protective zone might have a larger size because of a correspondingly long braking distance for the vehicle, so that the vehicle can be stopped in a timely manner once an object is detected in the protective zone for the vehicle and before a collision occurs. In contrast, if the vehicle is driving through a curve that is bordered by a wall or the like, the protective zone might have a smaller size, so that the wall is located outside of the protective zone. Otherwise, the detection of the wall within the protective zone would trigger an unnecessary emergency stop of the vehicle.
Known optical sensors cannot meet the requirement of adapting the protective zone, especially if the dimensions for a protective zone are fixedly preset in the optical sensor. German patent document DE 39 32 344 A1, for example, discloses an optical sensor of this type.
German patent document DE 199 15 509 A1 discloses an optical sensor embodied as a distance sensor for an area, which is provided with an evaluation unit capable of storing several protective zones. The protective zones can be selected and activated individually by means of several switches, so that the selected protective zone can be monitored to detect persons or objects entering this zone.